已知tanα=3,那么(sinα-2cosα)/(2sinα-cosα)=( )A. $\frac{1}{5}$B. -$\frac{1}{5}$C. $\fr
已知sin(α-β)=(1)/(3),cosαsinβ=(1)/(6),则cos(2α+2β)=( )A. $\frac{7}{9}$B. $\frac{1}{
已知sinα=-(3)/(5),且α是第三象限角,则cosα=( )A. -$\frac{2}{5}$B. -$\frac{4}{5}$C. $\frac{3}
7.[福建2020适应性模拟]已知 tan alpha =2 ,则-|||-dfrac ({sin )^2alpha -(cos )^2alpha +2}(2{
已知(sin )^2theta -(cos )^2theta =dfrac (2sqrt {2)}(3),求(sin )^2theta -(cos )^2the
若sin(α+β)+cos(α+β)=2sqrt(2)cos(α+(π)/(4))sinβ,则( )A. tan(α-β)=1B. tan(α+β)=1C. t
(int )_(0)^12xcos ((x)^2+1)dx= ( )A.cos 2- cos 1B.cos 2+ cos 1C.sin 2- sin 1D.si
若α∈(0,(π)/(2)),tan2α=(cosα)/(2-sinα),则tanα=( )A. $\frac{\sqrt{15}}{15}$B. $\frac
4.已知 sin alpha =-dfrac (3)(5), 且α是第三象限的角,则 cos alpha = __ ,-|||-tan alpha = __ o
[单选题] sum _(n=0)^infty ((-1))^ndfrac (2n+3)((2n+1)!)=A.sin1+cos1B.2sin1+cos1C.2s